In the manufacture of fiber reinforced plastic products, for many applications it is necessary that the resin dispersion throughout the product be uniform. If the resin to fiber ratio is too high, or too low, the products are unacceptable and must be rejected.
In the manufacture of fiber reinforced plastic products, fabric is woven from any of a number of fibers including glass, graphite, nylon, etc. The woven fabric is impregnated with resin, dried, formed into the final product shape (as by molding), and the resin is cured. It has been found, according to the present invention, that during the weaving of the fabrics, as a result of the natural strain provided on the warp threads, the edge areas become denser than the center area of the fabric. This happens as soon as the fabric is made and is especially noticeable once the fabric is removed from the loom. While the spacing of all of the warp yarns is originally uniform due to uniform spacing between the reed wires (that is uniform dents), after strain is removed, the warp threads in the edge areas of the fabric tend to move together. When such fabric is subsequently utilized to produce fiber reinforced plastic products, the fabric does not have uniform porosity therefore the resin dispersion after impregnation is non-uniform, and too high a percentage of rejects may be produced.
According to the present invention, a fiber reinforced plastic product is produced which has uniform resin dispersion throughout. The product according to the present invention is produced by the following method steps: (a) Weaving a fabric on a loom with warp ends and weft filling. (b) Varying the spacing between the warp ends at the edges of the fabric during weaving, compared to the warp ends at the centre of the fabric. (c) Removing the fabric from the loom such that as the strain on the warp and weft threads is relieved after removal of the fabric from the loom, the fabric has uniform porosity. (d) Imprenating the fabric with resin. (e) Drying the impregnated fabric. (f) Forming a final fiber reinforced plastic product having substantially uniform amounts of resin throughout its volume; and (g) curing the resin.
In the practice of the method according to the invention, one preferred manner of practicing step (b) is to provide a reed divided into a number of sections. For instance a center section, a pair of intermediate sections adjacent the center section, and a pair of edge sections adjacent the intermediate sections, may be provided. Within each section the reed dent size is uniform, and the dent size is also uniform within both edge sections and within both intermediate sections. The dent size in the edge sections is greater (e.g. 10-15 1,000ths of an inch) than the dent size in the intermediate sections, and the dent size in the intermediate sections is greater (e.g. about 10-15 1,000ths of an inch) than in the center section.
In addition, the fabric may be subjected to one or more finishing steps between steps (c) and (d).
According to the present invention a loom reed is also provided. The loom reed according to the invention comprises: a pair of frame portions, the frame portions being substantially parallel to each other and substantially co-extensive; a plurality of reed wires; and means for mounting the wires to the frame portions so that the wires extend substantially parallel to each other from one frame portion to the other, with dents fromed between the wires, with the dents at the end sections of the frame being larger than the dents at central portion of the frame. Agan, the reed is preferably formed into edge, intermediate, and central sections with the dent size as indicated above. Alternatively, the wires may vary in thickness to provide variable spacing of substantially equal dents.
It is the primary object of the present invention to produce fiber reinforced plastic products having uniform resin dispersion throughout, and a loom reed for facilitating the production of such products. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.